The invention relates to a head restraint of a vehicle seat, which is used as an energy absorber and whose absorption capacity can be influenced abruptly during an accident, in particular a rear-end accident. The invention also relates to a method of using the head rest and to a method of making the headrest.
The head restraints arranged on the vehicle seats have the task of intercepting the head of the vehicle occupants if, as a consequence of a rear-end impact, the head is flung rearwards. As this happens, the head covers a distance relative to the spinal column of the body, which distance can differ in length depending on the setting of the head restraint relative to the seat position of the vehicle occupants. It is clear that the risk of serious injuries in the region of the cervical spine is all the more pronounced the greater the distance to be covered by the head during the accident on account of the relative movement and the greater the difference between the movement of the body and of the head.
This risk is counteracted in the prior art by a series of solutions.
For example, German Published Patent Application DE 39 00 495 A1 discloses an arrangement in which a padded element is integrated into the head restraint, the padded element being driven either by a spring or pyrotechnically when a sensor emits a corresponding triggering signal when an accident occurs. The padded element then extends in the direction of the vehicle occupant""s head in order to reduce to the greatest possible extent the possible distance to be covered and thereby to support the back of the head.
Furthermore, European Published Patent Application EP 0 925 997 A2 discloses a head restraint which is moved forwards in the event of a rear-end impact in order to intercept the vehicle occupant""s head which is flung rearwards. To this end, at least one reservoir, which is filled with a flowable medium and is connected to a fillable element which is arranged in the head restraint, is arranged in the backrest of a vehicle seat, with the result that, in the event of a rear-end impact and as a function of the severity thereof, the flowable medium is displaced upwards by the upper part of the vehicle occupant""s body into the element of the head restraint, which then in consequence moves forwards in the direction of the occupant""s head.
Furthermore, German Patent Publication DE 297 10 511 U1 discloses a further solution in which a gas generator, which may optionally be arranged in the backrest of the vehicle seat, can act upon a corresponding gas bag, which is arranged in the head restraint, with a certain internal pressure, as a function of the impact intensity, in order to counteract the abovementioned risk of injury.
An object of the present invention is to provide a head restraint which, in comparison with the solutions from the prior art, offers improved absorption properties and whose use can be reversibly repeated as often as desired.
Furthermore, an object of the invention is to provide a head restraint which can be adapted individually, at all times in a repeatable and changeable manner, to the anatomical head shape of each individual vehicle occupant, with the result that it deploys optimum protective effects and is able to stabilize the head of the vehicle occupants, in particular during a rear-end impact.
According to the invention, these and other objects are achieved in that at least one container is integrated in the head restraint, the container being elastically deformable and being filled with filling bodies and being connected to means for the abrupt evacuation of the gas which is in it, by the formation of a negative pressure or vacuum.
The application of negative pressure means that a head restraint is available as a hard energy absorber having good absorption properties. At the same time, the vacuum ensures that the flexible covering of the container retains its shape even when subjected to a shock-like stress, as occurs through the impact of the head.
In an advantageous embodiment of the invention, the head restraint is coupled to a valve device which ensures that either negative pressure or ambient pressure prevails in the interior of the container. In the normal state, the interior of the container is acted upon by ambient pressure, so that the filling bodies which are situated in the container are loose and not tightly packed. This ensures a very soft dimensional flexibility of the head restraint which, moreover, can be set and adapted individually by the different degree of filling and different filling material.
In critical situations, however, it is not such a claim of comfort which is significant, but rather an efficient as possible energy absorption capacity of the head restraint. In the event of a rear-end impact, the interior of the container is abruptly acted upon by negative pressure or by a virtual vacuum, so that the filling bodies as a whole are compressed, in which case the elastic covering of the container is placed tightly against the filling bodies and the head restraint thereby becomes harder overall. The impacting head is therefore intercepted earlier, since it is no longer able to plunge into the head restraint and is therefore accelerated to a less severe extent in its rearwardly directed tilting movement.
The level of vacuum necessary depends on the specific design of the necessary hardness of the compacted container and ultimately on the material used for the filling bodies. In this connection, the ranges for the negative pressure or the virtual vacuum can lie within a range of about 30-700 mbar.
If a critical situation does not lead to the head impacting against the head restraint or against the container integrated therein, or the impact does not lead to a reversible changing of the container itself, then the latter may be refilled with air or acted upon by ambient pressure, with the result that the container does not become unusable and would have to be exchanged.
According to preferred embodiments of the invention, different principles and means can be used for generating the vacuum or negative pressure in the container. The means used can include vacuum pumps, optionally with vacuum reservoir containers coupled to them, and also overpressure containers using the Venturi principle or similar principles. The respective pressure states between the container and the vacuum-generating means can be maintained via a valve device.
Certain preferred embodiments of the invention are distinguished in that the means are coupled to a pre-crash sensory mechanism which triggers the respective negative-pressure or vacuum state only in extreme situations, as in particular in the case of a rear-end impact. In this case, it is possible to make recourse to a pre-crash sensory mechanism which is available in the vehicle and is already used for other active safety measures in the motor vehicle.
The head restraint according to certain preferred embodiments of the invention has a multiplicity of variables which permit, both individually and in each case independently of one another, and also in their entirety in concerted coordination with one another, individual adaptation both to the anatomical actuality of the vehicle occupant and also to the absorption properties required in the course of a rear-end accident.
The elasticity of the filling bodies which are used can therefore be selected as desired in accordance with the diversity of materials provided commercially. For example, the use of a jelly-like material which, in the event of a shock-like stress, collapses into itself and thereby makes available a path of deformation, is advantageous.
However, non-deformable, i.e., non-energy-absorbing materials, can be used as filling bodies, such as particular bulk material in the form of sand or powdery materials. The incompressible grains of sand result in the energy absorber in the form of the container functioning reversibly if the covering is not damaged.
Further examples of filling material which can be used include polypropylene in the form of spheres of differing density, or else wood dust or hollow glass spheres.
Further coordination can be obtained by differing the degree of filling of the container according to certain preferred embodiments of the invention. In further preferred embodiments, the gas-tight, elastic container is divided into a plurality of chambers, in which case the outer shape of the chambers and of the container, their size and the overall volume can be of different design for the purpose of optimum adaptation to the shape of the head restraint.
Strip-shaped, band-shaped, plate-shaped, round and angular chambers which are at least partially gas- and pressure-conductively connected to one another are provided according to certain preferred embodiments of the invention. Alternatively, the chambers are also completely sealed hermetically with respect to one another and each have a separate duct to the vacuum sources.
The container of certain preferred embodiments preferably comprises two films, one shaping film and one planar film, which can be adapted by means of thermoforming of the geometry of the head restraint. The films are welded or bonded to one another, in which case a connection for removing and filling with air is welded or bonded in at the same time. Polyurethane is preferably used here as the material for the films.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.